JP2008034138A - Direct methanol type fuel cell and methanol concentration adjusting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a direct methanol type fuel cell capable of easily adjusting the concentration of methanol supplied to the fuel cell at an appropriate concentration capable of demonstrating the power generation performance of the fuel cell to the maximum degree, and an adjusting method of the methanol concentration in the direct methanol type fuel cell. <P>SOLUTION: The direct methanol type fuel cell 1 is provided with a fuel cell body 2 and a concentration adjusting part 3 to adjust the concentration of methanol water solution. The concentration of methanol water solution can be adjusted by contacting the methanol water solution with the concentration adjusting part 3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a direct methanol fuel cell capable of generating electricity by directly supplying methanol as a fuel.

A solid polymer electrolyte fuel cell has a solid electrolyte membrane such as a perfluorosulfonic acid membrane as an electrolyte, and a fuel electrode and an oxidant electrode are joined to both sides of the membrane. Hydrogen or methanol is used for the anode and oxygen is used for the cathode. Is a device that generates electricity through an electrochemical reaction. Among these, solid polymer electrolyte fuel cells that use methanol as fuel are called “direct methanol fuel cells (DMFC)”. The electrochemical reaction that occurs at each electrode causes methanol to be used at the anode. If used,
CH ₃ OH + H ₂ O → 6H ^{+ +} CO ₂ + 6e ⁻ ... [1]
And at the cathode,
3 / 2O ₂ + 6H ^{+ +} 6e ⁻ → 3H ₂ O ... [2]
It is. In order to cause this reaction, both electrodes are composed of a mixture of carbon fine particles carrying a catalyst substance and a solid polymer electrolyte.

  In such a direct methanol fuel cell, the methanol supplied to the anode passes through the pores in the electrode and reaches the catalyst. The methanol is decomposed by the catalyst, and the electrons in the reaction of the above reaction formula [1]. To generate hydrogen ions. The hydrogen ions reach the cathode through the electrolyte in the anode and the solid electrolyte membrane between the two electrodes, react with oxygen supplied to the cathode and electrons flowing from the external circuit, and water as shown in the above reaction formula [2]. Produce. On the other hand, electrons released from methanol are led to the external circuit through the catalyst carrier in the anode, and flow into the cathode from the external circuit. As a result, in the external circuit, electrons flow from the anode to the cathode and electric power is taken out.

  This direct methanol fuel cell using methanol as a fuel is highly likely to be applied as a portable small fuel cell, and in recent years, development has been activated as a next-generation secondary battery such as a portable computer or a cellular phone.

  In the direct methanol fuel cell, it is known that the concentration of the aqueous methanol solution supplied to the fuel cell affects the output from the direct methanol fuel cell. For example, if the methanol concentration is too high, a “crossover phenomenon” occurs in which methanol permeates from the fuel electrode to the air electrode, methanol oxidation occurs at the air electrode, and the output power of the direct methanol fuel cell decreases. There is a risk that. On the other hand, if the methanol concentration is too low, the amount of protons generated at the fuel electrode decreases, and the output power of the direct methanol fuel cell may be reduced. Thus, in a direct methanol fuel cell, it is necessary to stably supply an aqueous methanol solution with an appropriate concentration to the fuel electrode without reducing the power generation performance of the fuel cell.

  In general, since fuel cells for portable devices are required to be miniaturized, an aqueous methanol solution having a concentration higher than the appropriate concentration in the fuel cell is used as fuel for the purpose of reducing the volume of the fuel cell. It is hoped that. Therefore, as a method for adjusting the methanol concentration of the fuel, a method of mixing a high concentration methanol fuel and water has been proposed.

  However, in the above method, the concentration adjusting tank for mixing the high concentration methanol fuel and water, the concentration sensor for measuring the methanol concentration in the concentration adjusting tank, and the pump 2 capable of adjusting the flow rates of the high concentration methanol fuel and water, respectively. A stand and a control device for controlling the driving of these pumps are required, which increases the cost of the fuel cell device and increases the size of the fuel cell device. In addition, in order to adjust the concentration of the aqueous methanol solution to an appropriate concentration that can maximize the power generation performance of the fuel cell, there is a problem that the control by the control device needs to be severely performed.

  The present invention has been made in view of such circumstances, and it is easy to adjust the concentration of methanol supplied to a fuel cell to an appropriate concentration that can maximize the power generation performance of the fuel cell. It is an object of the present invention to provide a direct methanol fuel cell that can be used and a method for adjusting the methanol concentration in the direct methanol fuel cell.

  In order to solve the above problems, the present invention includes a fuel cell main body and a concentration adjusting unit that adjusts the concentration of the aqueous methanol solution. By introducing the aqueous methanol solution into the concentration adjusting unit, the concentration of the aqueous methanol solution is increased. A direct methanol fuel cell is provided that can be adjusted (claim 1).

  According to the above invention (invention 1), the methanol concentration of the methanol aqueous solution can be easily adjusted to a concentration at which appropriate output power can be obtained from the fuel cell simply by introducing the methanol aqueous solution into the concentration adjusting unit and bringing it into contact with the concentration adjusting unit. In addition, since it is not necessary to provide a control device or the like for adjusting the methanol concentration, the configuration of the direct methanol fuel cell can be simplified.

  In the said invention (invention 1), the said density | concentration adjustment part is a substance for concentration adjustment containing the molecular compound which can take in methanol molecule selectively, Methanol aqueous solution is the said substance for concentration adjustment | control substance containing part It is preferable that the aqueous methanol solution is brought into contact with the molecular compound (claim 2).

  According to the above invention (Invention 2), when the aqueous methanol solution and the molecular compound come into contact with each other, the methanol molecules in the aqueous methanol solution are selectively taken into the molecular compound, so that the methanol concentration in the aqueous methanol solution can be easily adjusted. it can.

  In the above invention (invention 2), the molecular compound filled in the concentration-adjusting substance container may be a molecular compound incorporating methanol molecules, or a molecular compound not incorporating methanol molecules. Alternatively, it may be a mixture of a molecular compound incorporating methanol molecules and a molecular compound not incorporating methanol molecules (Claim 3).

  When the concentration of methanol fuel for fuel cells stored in the fuel tank is higher than the appropriate concentration, molecular compounds that have not taken in methanol molecules can be used to take in excess methanol molecules. Further, the concentration of the aqueous methanol solution can be adjusted to a concentration at which an appropriate output can be obtained from the fuel cell. On the other hand, when the concentration of methanol fuel for the fuel cell stored in the fuel tank is lower than the appropriate concentration, by using a molecular compound that has taken in methanol molecules, the insufficient methanol can be removed from the molecular compounds. The concentration of the aqueous methanol solution can be adjusted to a concentration at which an appropriate output can be obtained from the fuel cell. Therefore, according to the above invention (invention 3), an aqueous methanol solution having an appropriate concentration can be stably supplied to the fuel cell (fuel electrode). Note that the mixing ratio of the molecular compound taking in methanol and the molecular compound not taking in methanol molecules may be appropriately adjusted according to the methanol concentration in the fuel tank.

  In the said invention (invention 2 and 3), it is preferable that the said molecular compound is an inclusion compound which can include methanol molecule as a guest molecule (invention 4). According to the invention (Claim 4), the clathrate compound capable of clathrating methanol molecules as guest molecules takes in and releases methanol molecules by chemical equilibrium between the clathrate compound and the surrounding methanol aqueous solution. By bringing the aqueous methanol solution into contact with the clathrate compound, the concentration of the aqueous methanol solution can be easily adjusted by the concentration at which appropriate output power can be obtained from the fuel cell.

  Moreover, in the said invention (invention 1), the said density | concentration adjustment part can be made into the permeation | transmission membrane of 1 or 2 or more from which the transmittance | permeability of methanol and the transmittance | permeability of water differ (invention 5).

  According to the above invention (invention 5), since the concentration adjusting unit is a permeable membrane in which the permeability of methanol and the permeability of water are different, the methanol concentration of the high-concentration methanol aqueous solution in contact with the permeable membrane is changed to a fuel cell. Therefore, it is possible to adjust the concentration so that an appropriate output power can be obtained. Moreover, even when the difference in permeability between methanol and water in the permeable membrane is small, the difference in transmittance between methanol and water can be achieved by stacking a plurality of permeable membranes or arranging a plurality of permeable membranes in series. And the methanol concentration of the high-concentration aqueous methanol solution can be adjusted to a concentration at which appropriate output power can be obtained from the fuel cell.

  In the above invention (invention 5), it is preferable that at least one of the permeable membranes is a solid polymer electrolyte membrane (invention 6). The solid polymer electrolyte membrane is generally used as an electrolyte membrane provided between a fuel electrode and an air electrode of a direct methanol fuel cell, and the permeability of methanol and water is known in detail. According to the invention (Claim 6), the concentration of the aqueous methanol solution can be easily adjusted by the concentration capable of obtaining appropriate output power from the fuel cell.

  Furthermore, in the said invention (invention 1), the said concentration adjustment part is made into the adsorption substance accommodating part filled with the adsorption substance which has methanol adsorption ability, methanol aqueous solution is introduce | transduced into the said adsorption substance accommodating part, and methanol aqueous solution is adsorbed It can be made to contact a substance (Claim 7).

  According to the above invention (invention 7), an adsorbent having methanol adsorption ability and a high-concentration aqueous methanol solution come into contact with each other, and methanol is adsorbed on the adsorbent, so that the concentration of the aqueous methanol solution can be appropriately adjusted from the fuel cell. The density can be adjusted to obtain output power.

  In the said invention (invention 7), it is preferable that the said adsorption substance is 1 type, or 2 or more types chosen from a zeolite, silica, molecular sieve, activated carbon, clay minerals, and porous glass (invention). Item 8).

  According to the above invention (invention 8), zeolite, silica, molecular sieve, activated carbon, clay minerals, porous glass and the like have a high methanol adsorption capacity, so that the methanol concentration of the aqueous methanol solution can be more easily adjusted to the fuel cell. Therefore, it is possible to adjust the concentration so that an appropriate output power can be obtained.

  The present invention also provides a fuel cell main body, a concentration-adjusting substance container filled with a molecular compound capable of selectively taking in methanol molecules, one or two or more different methanol permeability and water permeability. A concentration adjusting unit comprising at least two kinds of adsorbing substance containing parts filled with a permeable membrane and an adsorbing substance having methanol adsorbing capacity, and introducing a methanol aqueous solution into the concentration adjusting part, thereby It is possible to provide a direct methanol fuel cell characterized in that the above-described adjustment is possible.

  According to the above invention (invention 9), the concentration of the methanol concentration in the aqueous methanol solution can be appropriately adjusted from the fuel cell by combining at least two types of the concentration adjusting substance containing part, the permeable membrane, and the adsorbing substance containing part as the concentration adjusting part. Can be easily adjusted according to the concentration at which a high output power can be obtained. In particular, by combining the concentration adjusting substance containing portion with the permeable membrane and / or the adsorbing substance containing portion, the permeable membrane and / or the adsorbing substance is methanol even when the molecular compound cannot take up methanol molecules. And the concentration of the aqueous methanol solution can be adjusted to a concentration at which appropriate output power can be obtained from the fuel cell.

  In the said invention (invention 1-9), it is preferable that the said density | concentration adjustment part is provided so that replacement | exchange is possible (invention 10). According to this invention (Claim 10), even if the function of adjusting the methanol concentration of the concentration adjusting unit is lowered, it is possible to obtain a stable concentration directly in the methanol fuel cell by simply replacing the concentration adjusting unit. An aqueous methanol solution can be supplied.

  The present invention also relates to a method for adjusting the methanol concentration of an aqueous methanol solution directly supplied to a methanol fuel cell, wherein the methanol concentration of the aqueous methanol solution is adjusted by bringing the aqueous methanol solution into contact with the concentration adjusting unit. A characteristic methanol concentration adjustment method is provided (claim 11).

  According to the above invention (invention 11), the concentration of the methanol aqueous solution can be easily adjusted to a concentration at which appropriate output power can be obtained from the fuel cell only by bringing the aqueous methanol solution into contact with the concentration adjusting unit. .

  In the said invention (invention 11), it is preferable to contact methanol aqueous solution with the molecular compound which can selectively take in a methanol molecule (invention 12).

  According to the above invention (invention 12), by bringing a methanol aqueous solution into contact with a molecular compound that can selectively take in methanol molecules, the methanol molecules in the methanol aqueous solution are selectively taken into the molecular compound, and methanol The concentration of the aqueous solution can be easily adjusted to a concentration at which appropriate output power can be obtained directly from the methanol fuel cell.

  In the above invention (invention 12), the molecular compound may be a molecular compound incorporating methanol molecules, a molecular compound not incorporating methanol molecules, or incorporating methanol molecules. It is also possible to use a mixture of a molecular compound that does not incorporate methanol molecules (claim 13).

  According to the above invention (invention 13), the aqueous methanol solution is brought into contact with a mixture of a molecular compound incorporating methanol molecules and a molecular compound not incorporating methanol molecules, so that the concentration of the aqueous methanol solution is appropriate from the fuel cell. If the concentration is higher than the concentration at which a sufficient output power can be obtained, the methanol molecules are taken into the molecular compound that has not taken in the methanol molecules in the mixture of molecular compounds, and the concentration of the methanol aqueous solution is adjusted to the appropriate output power from the fuel cell. When the concentration of the aqueous methanol solution is lower than the concentration at which proper output power can be obtained from the fuel cell, methanol is released from the molecular compound incorporating the methanol molecules. Get the proper output power from the fuel cell, the concentration of methanol aqueous solution It can be adjusted to a concentration capable of and.

  In the said invention (invention 12 and 13), it is preferable that the said molecular compound is an inclusion compound which can include methanol molecule as a guest molecule (invention 14). According to the invention (Claim 14), the clathrate compound that can clathrate methanol molecules as guest molecules takes up and releases methanol molecules by chemical equilibrium between the clathrate compound and the surrounding methanol aqueous solution. By bringing the aqueous methanol solution into contact with the clathrate compound, the concentration of the aqueous methanol solution can be easily adjusted by the concentration at which appropriate output power can be obtained from the fuel cell.

  In the above invention (invention 11), the methanol aqueous solution can be brought into contact with one or more permeable membranes having different methanol permeability and water permeability (invention 15).

  According to the above invention (invention 15), the concentration of the aqueous methanol solution can be adjusted to a concentration at which appropriate output power can be obtained from the fuel cell only by bringing the aqueous methanol solution into contact with the permeable membrane. Moreover, even when the difference in permeability between methanol and water in the permeable membrane is small, the difference in transmittance between methanol and water can be achieved by stacking a plurality of permeable membranes or arranging a plurality of permeable membranes in series. And the methanol concentration of the high-concentration aqueous methanol solution can be adjusted to a concentration at which appropriate output power can be obtained from the fuel cell.

  In the above invention (invention 15), it is preferable that at least one of the permeable membranes is a solid polymer electrolyte membrane (invention 16). The solid polymer electrolyte membrane is generally used as an electrolyte membrane provided between a fuel electrode and an air electrode of a direct methanol fuel cell, and the permeability of methanol and water is known in detail. According to the invention (invention 16), the concentration of the aqueous methanol solution can be easily adjusted by the concentration capable of obtaining appropriate output power from the fuel cell.

  In the said invention (invention 11), methanol aqueous solution can be made to contact the adsorption substance which has methanol adsorption ability (invention 17). According to this invention (invention 17), methanol is adsorbed on the adsorbent by bringing the adsorbent having methanol adsorption ability into contact with the high-concentration methanol aqueous solution, and the concentration of the methanol aqueous solution is appropriately output from the fuel cell. The density can be adjusted to obtain electric power.

  In the said invention (invention 17), it is preferable that the said adsorption substance is 1 type, or 2 or more types chosen from a zeolite, silicas, molecular sieve, activated carbon, clay minerals, and porous glass (invention). Item 18).

  According to the above invention (invention 18), zeolite, silica, molecular sieve, activated carbon, clay minerals, porous glass and the like have high methanol adsorbing ability, so that the methanol concentration of the aqueous methanol solution can be more easily adjusted to the fuel cell. Therefore, it is possible to adjust the concentration so that an appropriate output power can be obtained.

  The present invention provides at least two of a molecular compound capable of selectively taking in methanol molecules, one or more permeable membranes having different methanol permeability and water permeability, and an adsorbent having methanol adsorption ability. A methanol concentration adjusting method in a direct methanol fuel cell is provided, wherein the concentration of the methanol aqueous solution is adjusted by bringing a methanol aqueous solution into contact with the type (claim 19).

  According to the above invention (invention 19), the methanol concentration of the methanol aqueous solution can be obtained from the fuel cell with the proper output power by bringing the methanol aqueous solution into contact with at least two of the molecular compound, the permeable membrane and the adsorbing substance. The concentration can be easily adjusted. In particular, by contacting an aqueous methanol solution with the molecular compound and the permeable membrane and / or adsorbent, the permeable membrane and / or adsorbent captures the methanol even when the molecular compound fails to capture the methanol molecules. And since the density | concentration of methanol aqueous solution can be adjusted to the density | concentration which can obtain appropriate output electric power from a fuel cell, it is preferable.

  According to the present invention, there is provided a direct methanol fuel cell capable of easily adjusting the concentration of methanol supplied to a direct methanol fuel cell to an appropriate concentration that can maximize the performance of the fuel cell. be able to.

[First Embodiment]
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a first embodiment of the invention will be described with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a direct methanol fuel cell according to the present embodiment, and FIG. 2 is a graph showing changes in methanol concentration in the direct methanol fuel cell according to the present embodiment.

  As shown in FIG. 1, a direct methanol fuel cell 1 according to this embodiment includes a fuel electrode 2 having a fuel electrode 21, a solid polymer electrolyte membrane 22 and an air electrode 23, and a fuel electrode 21 of the fuel cell 2. The concentration adjusting substance storage 3 connected to the fuel supply tank 5, the supply fuel tank 5 connected upstream of the concentration adjusting substance storage 3 via the first pump 4, and the second pump 6 to the supply fuel tank 5. And a high-concentration fuel tank 7 connected to each other.

  The high concentration fuel tank 7 stores a methanol aqueous solution having a concentration higher than the concentration at which the output power value from the direct methanol fuel cell 1 can be maintained at an appropriate value (hereinafter referred to as “appropriate concentration”). The methanol concentration of the aqueous methanol solution stored in the high concentration fuel tank 7 is preferably 40 to 100% by mass.

  The supply fuel tank 5 is connected to the discharge port of the fuel electrode 21. The supply fuel tank 5 temporarily stores the aqueous methanol solution supplied from the high-concentration fuel tank 7, and the reaction at the fuel electrode 21. Thus, surplus fuel (unreacted methanol aqueous solution) in which methanol has been consumed is introduced.

  The concentration adjusting substance storage unit 3 is filled with a molecular compound capable of selectively taking in methanol molecules. The molecular compound filled in the concentration-adjusting substance storage unit 3 may be only a molecular compound that does not incorporate methanol molecules, may be only a molecular compound that incorporates methanol molecules, or may contain methanol molecules. It may be a mixture of a molecular compound that has not been incorporated and a molecular compound that has incorporated methanol molecules. The mixing ratio of the molecular compound that has not taken in the methanol molecules and the molecular compound that has taken in the methanol molecules can be appropriately adjusted according to the concentration of the aqueous methanol solution stored in the high concentration fuel tank 7.

  In the present embodiment, the molecular compound is a compound that can bind to methanol by a relatively weak interaction other than a covalent bond represented by hydrogen bond, van der Waals force, etc., and is a hydrate, solvate, addition compound, Inclusion compounds and the like are included. Such a molecular compound can be formed by a contact reaction between a compound that forms the molecular compound and methanol, and can convert gaseous or liquid methanol into a solid compound, which is relatively lightweight and stable. Methanol can be stored.

  As a molecular compound in the present embodiment, an inclusion compound capable of inclusion of methanol by a contact reaction between a host compound and methanol is preferable. In the methanol clathrate compound, there is a chemical equilibrium between the methanol concentration in the clathrate compound and the methanol concentration in the methanol aqueous solution around the clathrate compound, so the methanol concentration in the methanol aqueous solution is higher than the equilibrium concentration. In this case, methanol is included in the host compound to form a methanol inclusion compound, and the methanol concentration of the aqueous methanol solution is lowered. On the other hand, when the methanol concentration of the aqueous methanol solution is lower than the equilibrium concentration, methanol is released from the methanol clathrate compound, and the methanol concentration of the aqueous methanol solution increases. In this way, the methanol concentration of the aqueous methanol solution supplied to the fuel electrode 21 can be stably maintained so that appropriate output power can be obtained directly from the methanol fuel cell 1.

  As host compounds that form clathrate compounds containing methanol, those composed of organic compounds, inorganic compounds, and organic / inorganic composite compounds are known. Molecular hosts and the like are known.

  Examples of the monomolecular host include cyclodextrins, crown ethers, cryptands, cyclophanes, azacyclophanes, calixarenes, cyclotriveratrylenes, spherands, and cyclic oligopeptides.

  Multimolecular hosts include ureas, thioureas, deoxycholic acids, cholic acids, perhydrotriphenylenes, tri-o-thymotides, bianthryls, spirobifluorenes, cyclophosphazenes, monoalcohols Diols, hydroxybenzophenones, acetylene alcohols, phenols, bisphenols, trisphenols, tetrakisphenols, polyphenols, naphthols, bisnaphthols, diphenylmethanols, carboxylic acid amides, thioamides, bixanthenes , Carboxylic acids, imidazoles, hydroquinones and the like.

  Examples of the polymer host include celluloses, starches, chitins, chitosans, polyvinyl alcohols, polyethylene glycol arm polymers having 1,1,2,2, -tetrakisphenylethane as a core, α, α, Examples include polyethylene glycol arm type polymers having α ′, α′-tetrakisphenylxylene as a core. In addition, organophosphorus compounds, organosilicon compounds, and the like are also included.

  Examples of the inorganic host compound include titanium oxide, graphite, alumina, transition metal dicargogenite, lanthanum fluoride, clay mineral (montmorillonite, etc.), silver salt, silicate, phosphate, zeolite, silica, porous glass, etc. It is done.

  Furthermore, some organometallic compounds exhibit properties as host compounds. For example, organoaluminum compounds, organotitanium compounds, organoboron compounds, organozinc compounds, organoindium compounds, organogallium compounds, organotellurium compounds, organotins. Examples thereof include compounds, organic zirconium compounds, and organic magnesium compounds. In addition, a metal salt of an organic carboxylic acid, an organic metal complex, or the like can be used as the host compound, but the organic metal compound is not particularly limited thereto.

  Of these host compounds, multimolecular hosts whose inclusion ability is less affected by the molecular size of the guest compound are more effective.

  Specific examples of the multimolecular host compound include urea, 1,1,6,6-tetraphenylhexa-2,4-diyne-1,6-diol, and 1,1-bis (2,4-dimethyl). Phenyl) -2-propyn-1-ol, 1,1,4,4-tetraphenyl-2-butyne-1,4-diol, 1,1,6,6-tetrakis (2,4-dimethylphenyl)- 2,4-hexadiyne-1,6-diol, 9,10-diphenyl-9,10-dihydroanthracene-9,10-diol, 9,10-bis (4-methylphenyl) -9,10-dihydroanthracene- 9,10-diol, 1,1,2,2-tetraphenylethane-1,2-diol, 4-methoxyphenol, 2,4-dihydroxybenzophenone, 4,4′-dihydroxybenzophenone, 2 2 ′, 4,4′-tetrahydroxybenzophenone, 1,1-bis (4-hydroxyphenyl) cyclohexane, 4,4′-sulfonylbisphenol, 2,2′-methylenebis (4-methyl-6-tert-butylphenol) 4,4′-ethylidenebisphenol, 4,4′-thiobis (3-methyl-6-tert-butylphenol), 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) Butane, 1,1,2,2-tetrakis (4-hydroxyphenyl) ethane, 1,1,2,2-tetrakis (4-hydroxyphenyl) ethylene, 1,1,2,2-tetrakis (3-methyl- 4-hydroxyphenyl) ethane, 1,1,2,2-tetrakis (3-fluoro-4-hydroxyphenyl) ethane, α, α, α ′, α′-te Trakis (4-hydroxyphenyl) -p-xylene, 3,6,3 ′, 6′-tetramethoxy-9,9′-bi-9H-xanthene, 3,6,3′6′-tetraacetoxy-9, 9′-bi-9H-xanthene, gallic acid, methyl gallate, catechin, bis-β-naphthol, α, α, α ′, α′-tetraphenyl-1,1′-biphenyl-2,2′-di Methanol, bis (dicyclohexylamide) diphenate, bis (dicyclohexylamide) fumarate, cholic acid, deoxycholic acid, 1,1,2,2-tetrakis (4-carboxyphenyl) ethane, 1,1,2,2- Tetrakis (3-carboxyphenyl) ethane, acetylenedicarboxylic acid, 2,4,5-triphenylimidazole, 1,2,4,5-tetraphenylimidazole, 2-phenyl Nylphenanthro [9,10-d] imidazole, 2- (o-cyanophenyl) phenanthro [9,10-d] imidazole, 2- (m-cyanophenyl) phenanthro [9,10-d] imidazole, 2- (p -Cyanophenyl) phenanthro [9,10-d] imidazole, hydroquinone, 2-t-butylhydroquinone, 2,5-di-t-butylhydroquinone, 2,5-bis (2,4-dimethylphenyl) hydroquinone, etc. However, a phenolic host compound such as 1,1-bis (4-hydroxyphenyl) cyclohexane is advantageous in that it can be used industrially.

  These host compounds may be used individually by 1 type, and may use 2 or more types together. These host compounds may be compounds of any shape as long as they form a solid inclusion compound with methanol.

  The organic host compound described above can also be used as an organic / inorganic composite material supported on an inorganic porous material. In this case, examples of the porous material supporting the organic host compound include silica, zeolites, activated carbons, intercalation compounds such as clay minerals and montmorillonites, but are not limited thereto. Absent.

  As a method for producing such an organic / inorganic composite material, the above organic host compound is dissolved in a solvent that can be dissolved, the solution is impregnated in an inorganic porous material, and the solvent is dried, dried under reduced pressure, or the like. Can be manufactured. Although there is no restriction | limiting in particular as the load of the organic host compound with respect to an inorganic porous material, Usually, it is about 0.1-80 mass% with respect to an inorganic porous material.

  In such a direct methanol fuel cell 1, when the operation of the direct methanol fuel cell 1 is started, the methanol aqueous solution in the high concentration fuel tank 7 is supplied to the supply fuel tank 5 by the second pump 6. At this time, since only the methanol aqueous solution in the high concentration fuel tank 7 is supplied into the supply fuel tank 5, the methanol aqueous solution having a methanol concentration higher than the appropriate concentration is stored in the supply fuel tank 5. (Points A to B in the graph of FIG. 2).

  The aqueous methanol solution in the supply fuel tank 5 is supplied to the concentration adjusting substance storage unit 3 by the first pump 4. The aqueous methanol solution supplied to the concentration adjusting substance storage unit 3 comes into contact with the inclusion compound filled in the concentration adjusting substance storage unit 3, and methanol molecules in the aqueous methanol solution are selectively included, so that the methanol aqueous solution The methanol concentration is adjusted to an appropriate concentration (D point to E point in the graph of FIG. 2).

The aqueous methanol solution whose concentration is adjusted in the concentration adjusting substance storage unit 3 is supplied to the fuel electrode 21. When the aqueous methanol solution is supplied to the fuel electrode 21, methanol is converted into hydrogen ions (H ⁺ ), carbon dioxide (CO ₂ ), and electrons (e ⁻ ) by the catalyst component of the fuel electrode 21. Converted. Electrons (e ⁻ ) are introduced from the external circuit (not shown) by electrical connection, and hydrogen ions (H ⁺ ) pass through the solid polymer electrolyte membrane 22 to be introduced into the air electrode 23. Air (or oxygen (O ₂ )) is supplied to the air electrode 23, and this oxygen (O ₂ ) reacts with hydrogen ions (H ⁺ ) and electrons (e ⁻ ) generated at the fuel electrode 21 to generate water. Arise. In such a reaction, electrons (e ⁻ ) flow from the fuel electrode 21 toward the air electrode 23 to extract electric power. Thus, in the direct methanol fuel cell 1, an appropriate voltage is output from the direct methanol fuel cell 1 without causing a crossover phenomenon.

  Excess methanol aqueous solution is discharged from the discharge port of the fuel electrode 21 and introduced into the supply fuel tank 5. Since the methanol aqueous solution is supplied from the high concentration fuel tank 7 to the supply fuel tank 5, the excess methanol aqueous solution returned from the fuel electrode 21 and the methanol aqueous solution in the high concentration fuel tank 7 are supplied in the supply fuel tank 5. Are mixed.

  If the methanol fuel cell 1 is continuously operated and the methanol aqueous solution in the high concentration fuel tank 7 becomes empty, the methanol aqueous solution is not supplied from the high concentration fuel tank 7 to the supply fuel tank 5.

  On the other hand, since the surplus methanol aqueous solution returned from the fuel electrode 21 continues to be supplied to the supply fuel tank 5, the methanol concentration of the methanol aqueous solution in the supply fuel tank 5 gradually decreases (B in the graph of FIG. 2). Point to point C), the methanol concentration of the aqueous methanol solution supplied from the supply fuel tank 5 to the concentration-adjusting substance storage unit 3 decreases.

  When the methanol concentration in the methanol aqueous solution supplied from the supply fuel tank 5 to the concentration adjusting substance storage unit 3 becomes lower than the equilibrium concentration, methanol is released from the methanol clathrate compound into the methanol aqueous solution, and the methanol having an appropriate concentration is obtained. The aqueous solution is supplied to the fuel electrode 21 (points E to F in the graph of FIG. 2).

  If the operation is continued as it is, the methanol concentration in the fuel electrode 21 gradually decreases, and the direct methanol fuel cell 1 is properly used until the use limit concentration of the direct methanol fuel cell 1 is exceeded (point G in the graph of FIG. 2). Can drive to.

  In the present embodiment, as a means for adjusting the methanol concentration, the concentration adjusting substance containing portion 3 filled with a host compound capable of forming a molecular compound with methanol has been described as an example. However, the present invention is not limited to this. For example, membranes having different methanol permeability and water permeability may be used. In this case, it is preferable to use a permeable membrane in which the water permeability is at least twice that of methanol. As such a permeable membrane, the fuel electrode and air electrode of a direct methanol fuel cell are generally used. It is preferable to use a solid polymer electrolyte membrane provided between the two. In this way, by providing the permeable membrane between the supply fuel tank 5 and the fuel electrode 21, water permeates more than methanol, so that the methanol concentration is lower than that of the aqueous methanol solution in the supply fuel tank 5. The aqueous solution is supplied to the fuel electrode 21. Only one such permeable membrane may be provided, or a plurality of permeable membranes may be provided.

  In addition, the concentration adjusting substance storage unit 3 may be filled with an adsorbing substance having a high methanol adsorbing capacity instead of the host compound. Since such an adsorbing substance is filled, methanol in the aqueous methanol solution supplied to the concentration adjusting substance housing unit 3 is temporarily adsorbed by the adsorbing substance, so that the aqueous methanol solution supplied to the fuel electrode 21 The methanol concentration can be adjusted to an appropriate concentration.

  Further, as the concentration adjusting means, the concentration adjusting substance accommodating unit 3 filled with the host compound, the above-described permeable membrane, and the concentration adjusting substance accommodating unit 3 filled with the adsorbing substance may be used in any combination. By combining these, the methanol concentration of the aqueous methanol solution can be adjusted more easily.

  Although the permeable membrane can selectively capture methanol but cannot release methanol, it is preferably used in combination with the concentration-adjusting substance containing unit 3 filled with the host compound. Thereby, even if it is a case where methanol could not be completely included by the host compound filled in the concentration adjusting substance housing part 3, the methanol is captured by the permeable membrane, and the methanol concentration is adjusted to an appropriate concentration. Can do. Further, since the adsorbing substance does not have the same methanol retention as the host compound, any adsorbing substance having a high adsorption / desorption rate can be used as a means for assisting the host compound.

  As described above, in the direct methanol fuel cell 1 according to the present embodiment, since the methanol molecules in the methanol aqueous solution are included by the host compound, the concentration of the methanol aqueous solution supplied to the fuel electrode 21 is easily adjusted to an appropriate concentration. When the concentration of the aqueous methanol solution becomes lower than the appropriate concentration, methanol is released from the host compound that includes the methanol molecules, so that the concentration of the aqueous methanol solution supplied to the fuel electrode 21 can be easily adjusted to the appropriate concentration. can do. Thereby, compared with the conventional direct methanol fuel cell, it can continue supplying methanol aqueous solution of appropriate concentration for a long time, and it is also possible to extend the time which can operate this fuel cell appropriately.

[Second Embodiment]
A second embodiment of the present invention will be described with reference to the drawings.
FIG. 3 is a schematic configuration diagram of the direct methanol fuel cell according to the present embodiment, and FIG. 4 shows the transition of the methanol concentration in the direct methanol fuel cell according to the present embodiment and the conventional direct methanol fuel cell. It is a graph.

  The direct methanol fuel cell 10 according to this embodiment includes a fuel cell 20 having a fuel electrode 201, a solid polymer electrolyte membrane 202 and an air electrode 203, and a fuel layer 30 provided so as to be in contact with the fuel electrode 201. Prepare. The fuel cell 20 having the fuel electrode 201, the solid polymer electrolyte membrane 202, and the air electrode 203 may be the same as that of the first embodiment.

  The fuel layer 30 stores a high-concentration aqueous methanol solution. The methanol concentration of the aqueous methanol solution stored in the fuel layer 30 may be 40 to 100% by mass, for example. The fuel layer 30 is prefilled with a host compound 50 that is not clathrated with methanol. The host compound filled in the fuel layer 30 may be the same as the host compound in the first embodiment.

  The filling amount of the host compound in the fuel layer 30 may be an amount that can adjust the methanol concentration of the aqueous methanol solution supplied to the fuel electrode 201 to an appropriate concentration, and the methanol concentration of the aqueous methanol solution stored in the fuel layer 30. It may be adjusted as appropriate according to the capacity and capacity.

  In such a direct methanol fuel cell 10, first, an aqueous methanol solution is filled in the fuel layer 30. When the methanol aqueous solution is filled in the fuel layer 30, the methanol in the methanol aqueous solution is included in the host compound filled in advance. Since the methanol concentration of the aqueous methanol solution filled in the fuel layer 30 is higher than the appropriate concentration (point A in the graph of FIG. 4), the methanol is included in the host compound, so that the inside of the fuel layer 30 The methanol concentration of the methanol aqueous solution can be adjusted to an appropriate concentration (point B in the graph of FIG. 4).

  When the direct methanol fuel cell 10 is continuously operated, the methanol in the fuel layer 30 is consumed, and the methanol concentration of the aqueous methanol solution in the fuel layer 30 decreases. Then, the methanol clathrated in the methanol clathrate compound is released into the aqueous methanol solution, and an aqueous methanol solution with an appropriate concentration is supplied to the fuel electrode 201 (points C to D in the graph of FIG. 4). Thereby, the direct methanol fuel cell 10 can be stably operated for a long time.

  When the direct methanol fuel cell 10 is further operated, all the methanol in the fuel layer 30 is consumed, and the methanol concentration of the aqueous methanol solution supplied to the fuel electrode 201 gradually decreases (from point D in the graph of FIG. 4). F point), the direct methanol fuel cell 1 can be properly used until the use limit concentration is exceeded (point E in the graph of FIG. 4).

  On the other hand, in the conventional direct methanol fuel cell, the methanol concentration of the aqueous methanol solution supplied to the fuel electrode decreases with the operation of the direct methanol fuel cell. The concentration of the aqueous methanol solution is higher than the proper concentration (points A to G in FIG. 4), and a crossover phenomenon occurs. In the latter half of the operation, the methanol concentration becomes lower than the proper concentration (graph H in FIG. 4). The output power from the direct methanol fuel cell is insufficient.

  Thus, the direct methanol fuel cell 10 according to the present embodiment supplies the methanol aqueous solution adjusted to an appropriate concentration by reducing the methanol concentration of the aqueous methanol solution to the fuel electrode 201 from the initial startup to the first half of operation. From the latter half of the operation, the methanol aqueous solution adjusted to an appropriate concentration by increasing the methanol concentration of the aqueous methanol solution can be supplied to the fuel electrode 21, so that it is appropriate for a long time compared to the conventional direct methanol fuel cell. Can drive easily.

  As described above, the direct methanol fuel cell according to the present embodiment can easily adjust the concentration of methanol supplied to the fuel cell to an appropriate concentration that can maximize the performance of the fuel cell. it can. As a result, it is possible to extend the period during which the direct methanol fuel cell can be properly used without increasing the capacity of the tank for storing methanol as fuel.

  The embodiment described above is described for facilitating understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

  In the present embodiment, when the methanol concentration in the clathrate compound (molecular compound) becomes lower than a predetermined value, the amount of methanol released from the clathrate compound decreases, and accordingly the performance of the direct methanol fuel cells 1 and 10 also increases. In order to decrease, for example, the concentration of methanol supplied to the fuel electrode 21 and the output power value from the direct methanol fuel cells 1 and 10 are detected, and the high-concentration fuel tank 7 or fuel layer of the methanol aqueous solution is detected based on the detected value. It is also possible to notify the user of the direct methanol fuel cells 1 and 10 of the supplement to 30 or the like.

1 is a schematic configuration diagram of a direct methanol fuel cell according to a first embodiment of the present invention. It is a graph which shows transition of the methanol concentration in the direct methanol fuel cell which concerns on the 1st Embodiment of this invention. It is a schematic block diagram of the direct methanol fuel cell which concerns on the 2nd Embodiment of this invention. It is a graph which shows transition of the methanol concentration in the direct methanol fuel cell which concerns on the 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,10 ... Direct methanol fuel cell 2,20 ... Fuel cell (fuel cell main body)
3 ... Concentration adjusting substance container (concentration adjusting unit)

Claims (19)

A fuel cell body;
A concentration adjusting unit for adjusting the concentration of the aqueous methanol solution,
A direct methanol fuel cell, wherein the concentration of the aqueous methanol solution can be adjusted by bringing the aqueous methanol solution into contact with the concentration adjusting unit. The concentration adjusting unit is a concentration adjusting substance containing unit filled with a molecular compound capable of selectively taking in methanol molecules,
2. The direct methanol fuel cell according to claim 1, wherein an aqueous methanol solution is supplied to the concentration-adjusting substance container, and the aqueous methanol solution is brought into contact with the molecular compound.   The molecular compound filled in the substance for concentration adjustment is a molecular compound incorporating methanol molecules, a molecular compound not incorporating methanol molecules, or a molecule compound incorporating methanol molecules and a molecule not incorporating methanol molecules. 3. The direct methanol fuel cell according to claim 2, wherein the direct methanol fuel cell is a mixture with a compound.   4. The direct methanol fuel cell according to claim 2, wherein the molecular compound is an inclusion compound that can include methanol molecules as guest molecules. 5.   2. The direct methanol fuel cell according to claim 1, wherein the concentration adjusting unit is one or more permeable membranes having different methanol permeability and water permeability.   6. The direct methanol fuel cell according to claim 5, wherein at least one of the permeable membranes is a solid polymer electrolyte membrane. The concentration adjusting unit is an adsorbing substance storage unit filled with an adsorbing substance having methanol adsorption ability;
2. The direct methanol fuel cell according to claim 1, wherein an aqueous methanol solution is supplied to the adsorbent containing portion and the aqueous methanol solution is brought into contact with the adsorbent.   8. The direct methanol fuel according to claim 7, wherein the adsorbing material is one or more selected from zeolite, silicas, molecular sieves, activated carbons, clay minerals and porous glasses. battery. A fuel cell body;
Concentration-adjusting substance container filled with a molecular compound capable of selectively taking in methanol molecules, one or more permeable membranes having different methanol permeability and water permeability, and an adsorbent having methanol adsorption ability A concentration adjusting unit consisting of at least two of the adsorbent containing units filled with
A direct methanol fuel cell, wherein the concentration of the aqueous methanol solution can be adjusted by bringing the aqueous methanol solution into contact with the concentration adjusting unit.   The direct methanol fuel cell according to any one of claims 1 to 9, wherein the concentration adjusting unit is replaceably provided. A method for adjusting the methanol concentration of an aqueous methanol solution supplied directly to a methanol fuel cell,
A method for adjusting methanol concentration, comprising adjusting a methanol concentration of an aqueous methanol solution by bringing the aqueous methanol solution into contact with a concentration adjusting unit.   The methanol concentration adjusting method according to claim 11, wherein the methanol aqueous solution is brought into contact with a molecular compound capable of selectively taking in methanol molecules.   The molecular compound is a molecular compound incorporating methanol molecules, a molecular compound not incorporating methanol molecules, or a mixture of a molecular compound incorporating methanol molecules and a molecular compound not incorporating methanol molecules. The methanol concentration adjusting method according to claim 12.   The method for adjusting a methanol concentration according to claim 12 or 13, wherein the molecular compound is an inclusion compound that can include methanol molecules as guest molecules.   12. The methanol concentration adjusting method according to claim 11, wherein the methanol aqueous solution is brought into contact with one or more permeable membranes having different methanol permeability and water permeability.   The method for adjusting methanol concentration according to claim 15, wherein at least one of the permeable membranes is a solid polymer electrolyte membrane.   The methanol concentration adjusting method according to claim 11, wherein the methanol aqueous solution is brought into contact with an adsorbent having methanol adsorption ability.   The method for adjusting methanol concentration according to claim 17, wherein the adsorbing material is one or more selected from zeolite, silicas, molecular sieves, activated carbons, clay minerals, and porous glasses. . Methanol aqueous solution for at least two kinds of molecular compounds capable of selectively taking in methanol molecules, one or more permeable membranes having different methanol permeability and water permeability, and adsorbents having methanol adsorption ability A method for adjusting the concentration of methanol in a direct methanol fuel cell, characterized in that the concentration of the aqueous methanol solution is adjusted by bringing the aqueous solution into contact with each other.

Images